shepherd:
"Over the centuries, the Greek language has exhibited a remarkable continuity and has evidenced far fewer variations than the English language has since the time of Chaucer (c. 1340-1400). [...] [I]t is probably no overstatement to observe that the student who can read either Xenophon's Anabasis or Plato's Apology will have little difficulty reading the New Testament or even a modern Greek newspaper (except for some different vocabulary)." (An Introductory Grammar of New Testament Greek, by Paul L. Kaufmam, Ph.D)
Interestingly, two scholars who disliked the Jehovah's Witnesses with passion, i.e. Julius Mantey and Walter Martin, both Baptists, had a conversation where Walter Martin, the so called "cult expert" was sort of mocking the NWT translators lack of Greek knowledge (their view of things), when Julius Mantey asked him about one of the translators Greek background (George Gangas).
J. Mantey asked Martin: "He was born in Greece, wasn't he?" Martin then answered: "Yes, he read modern Greek, and I met him when I visited the Watchtower." Of course, Martin went on to say that this Greek speaker did not know what "the subject" of the last clause of John 1:1c was.
That assertion about Gangas not knowing "the subject" is questionable in itself. But my point is that even Mantey who hated the JWs, acknowledge by his question that a NWT translator having a Greek background could make a difference in the translation process.